Abstract: In order to explore the influence of high salinity mine water (total dissolved solid content >1 g / L) containing chlorine on strength of cemented tailings backfill,taking tailings from a gold mine in Bohai Bay,Jiaodong Peninsula,China as aggregate,the compressive strength of backfill prepared by mixing slag-based cementing materials ( desulfurized gypsum and hydrated lime as activator) and tailings with high salinity mine water was tested. The hydration products of the slag-based binder and micro-structure of harden backfill were detected by X-ray diffractometer,scanning electron microscope and mercury porosimeter. The influence of variables (mass ratio of desulfurized gypsum / hydrated lime and slag dosage) on strength of backfill was analyzed. The results show that:① The introduced high salinity underground mine water containing chlorine promotes the formation of hydration products and optimizes the microstructure of backfill,thus obtaining the high-strength cemented tailings backfill. Ettringite and calcium silicate hydrate ( C—S—H) are two main hydration products,and no new hydration products are formed due to the incorporation of Cl-,Na+,Ca2+ and Mg2+ ions,but the effect on the molecular structure of C—S—H needs further study. ② The strength of backfill at each curing age increases first and then decreases with the increase of the ratio of desulfurized gypsum to hydrated lime,and the ratio of desulfurized gypsum to hydrated lime corresponding to each peak strength increases with the extension of curing time. However,the optimal slag content corresponding to the peak strength of different ages is always stable at 67. 8%. The proportion of desulfurized gypsum and hydrated lime can be adjusted to meet the time demand for the strength of backfill in specific engineering. The results of this study can provide theoretical basis and technical guidance for the application of high salinity mine water in the preparation of backfill materials for mines. The results ofthis study can provide theoretical basis and technical guidance for the application of high salinity mine water in the preparation of backfill materials for mines.